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Validation of a single-platform, volumetric, flow cytometry for CD4 T cell count monitoring in therapeutic mobile unit.

Mbopi-Kéou FX, Sagnia B, Ngogang J, Angwafo FF, Colizzi V, Montagnier L, Bélec L - J Transl Med (2012)

Bottom Line: A FACSCalibur flow cytometer (Becton Dickinson Immuno-cytometry System, San Jose, CA, USA) was used as reference method.Bland-Altman analysis showed a close agreement between Auto40 and FACSCalibur results expressed in absolute count as in percentage in Yaoundé and Ambang Bikok.The Auto40 flow cytometer installed in a therapeutic mobile unit and operated far from its reference laboratory gave a perfect correlation with the reference method, and could be useful in carrying out immunological monitoring of HIV-infected patients living in areas without access to laboratory facilities.

View Article: PubMed Central - HTML - PubMed

Affiliation: Laboratoire National de Santé Hygiène Mobile, Ministère de la Santé Publique, and Faculté de Médecine et des Sciences Biomédicales, Université de Yaoundé I, Yaoundé, Cameroun. fxmkeou@hotmail.com

ABSTRACT

Background: A mobile health unit may be useful to follow up adult and pediatric patients on antiretroviral treatment and living in remote areas devoid of laboratory facilities. The study evaluated the use of the simplified, robust, single-plateform, volumetric, pan-leucogating Auto40 flow cytometer (Apogee Flow Systems Ltd, Hemel Hempstead, UK) for CD4 T cell numeration in a mobile unit, compared against a reference flow cytometry method.

Methods: The therapeutic mobile unit of the Laboratoire National de Santé Hygiène Mobile, Yaoundé, Cameroon, was equipped with the Auto40. A FACSCalibur flow cytometer (Becton Dickinson Immuno-cytometry System, San Jose, CA, USA) was used as reference method. EDTA-blood samples from volunteers were first subjected to CD4 T cell count in the mobile unit, and an aliquot was sent within 4 hours to Centre International de Référence Chantal Biya, Yaoundé, for FACSCalibur assay.

Results: Two HIV screening campaigns with the mobile unit were organised in December 2009 and January 2010. The campaign in the suburb of Yaoundé which was 20 km from the reference laboratory included 188 volunteers comprising 93 children less than 5 years old. The campaign in Ambang Bikok (53 km far from Yaoundé) included 69 adult volunteers. In Yaoundé suburb, mean ± standard deviation (SD) CD4 T cell count was 996 ± 874 cells/μl by Auto40, and 989 ± 883 cells/μl by FACSCalibur; in Ambang Bikok, mean ± SD CD4 T cell count was 1041 ± 317 cells/μl by Auto40, and 1032 ± 294 cells/μl by FACSCalibur. Results by Auto40 and FACSCalibur were highly correlated in Yaoundé (r(2) = 0.982) as in Ambang Bikok (r(2) = 0.921). Bland-Altman analysis showed a close agreement between Auto40 and FACSCalibur results expressed in absolute count as in percentage in Yaoundé and Ambang Bikok. When pooling the 257 CD4 T cell count measurements, the Auto40 yielded a mean difference of +7.6 CD4 T cells/μl higher than by reference flow cytometry; and the sensitivity and specificity of Auto40 in enumerating absolute CD4 T cell counts of less than 200 cells/μl were 87% and 99%, respectively, and in enumerating absolute CD4 T cell counts of less than 350 cells/μl were 87% and 98%, respectively. The intrarun and interun precisions of the Auto40 assay assessed in the mobile unit were 5.5% and 7.9%, respectively.

Conclusions: The Auto40 flow cytometer installed in a therapeutic mobile unit and operated far from its reference laboratory gave a perfect correlation with the reference method, and could be useful in carrying out immunological monitoring of HIV-infected patients living in areas without access to laboratory facilities.

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Results of 93 CD4 T cell count measurements from children aged less than 5 years and more than 18 months in the suburb of Yaoundé, expressed in absolute number (cells/μl) and in percentage carried out in parallel by the Auto40 flow cytometer and by FACSCalibur. - A and C. Passing-Bablok agreement test between the CD4 T cell count results obtained with the Auto40 and FACSCalibur flow cytometers, in absolute number (A) and in percentage (C). The diagonal dotted line represents the ideal line (no bias). The full line represents the regression line of the distribution; - B and D. Bland-Altman analysis on the relative differences between the CD4 T cell counts obtained with the Auto40 and FACSCalibur flow cytometers compared with the average CD4 T cell count, in absolute number (B) and in percentage (C). The full line represents the mean relative difference, and the dotted lines represent the superior and inferior limits of agreement. The arrow corresponds to the X abscise axis.
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Figure 2: Results of 93 CD4 T cell count measurements from children aged less than 5 years and more than 18 months in the suburb of Yaoundé, expressed in absolute number (cells/μl) and in percentage carried out in parallel by the Auto40 flow cytometer and by FACSCalibur. - A and C. Passing-Bablok agreement test between the CD4 T cell count results obtained with the Auto40 and FACSCalibur flow cytometers, in absolute number (A) and in percentage (C). The diagonal dotted line represents the ideal line (no bias). The full line represents the regression line of the distribution; - B and D. Bland-Altman analysis on the relative differences between the CD4 T cell counts obtained with the Auto40 and FACSCalibur flow cytometers compared with the average CD4 T cell count, in absolute number (B) and in percentage (C). The full line represents the mean relative difference, and the dotted lines represent the superior and inferior limits of agreement. The arrow corresponds to the X abscise axis.

Mentions: The Figure 2 depicts the results from 93 CD4 T cell count measurements from children aged less than 5 years and more than 18 months, expressed in absolute number and in percentage. In this pediatric population, analysis of CD4 T cell count measurement expressed in percentage showed, similarly to CD4 T cell count expressed in absolute numbers, a high correlation and a close agreement between both CD4 T cell counting methods. Mean ± SD CD4 T cell count in percentage was 32.7 ± 12.1%CD4 (range, 10-70) by Auto40, and 33.0 ± 12.8%CD4 (range, 9-75) by FACSCalibur. The differences between Auto40 and FACSCAlibur were not statistically significant (P > 0.5). Results by Auto40 and FACSCalibur were highly correlated by regression analysis (r2 = 0.986, slope = 1.00, intercept = 0.0) (Figure 2, C). The relation between Auto40 and FACSCalibur did not differ from linearity (P > 0.5). The Auto40 results showed a bias of -0.30%CD4+ (95% CI: -0.91 - 0.31) as compared with FACSCalibur (Figure 2, C), thus demonstrating a close agreement between both methods to measure CD4 T cells in percentage.


Validation of a single-platform, volumetric, flow cytometry for CD4 T cell count monitoring in therapeutic mobile unit.

Mbopi-Kéou FX, Sagnia B, Ngogang J, Angwafo FF, Colizzi V, Montagnier L, Bélec L - J Transl Med (2012)

Results of 93 CD4 T cell count measurements from children aged less than 5 years and more than 18 months in the suburb of Yaoundé, expressed in absolute number (cells/μl) and in percentage carried out in parallel by the Auto40 flow cytometer and by FACSCalibur. - A and C. Passing-Bablok agreement test between the CD4 T cell count results obtained with the Auto40 and FACSCalibur flow cytometers, in absolute number (A) and in percentage (C). The diagonal dotted line represents the ideal line (no bias). The full line represents the regression line of the distribution; - B and D. Bland-Altman analysis on the relative differences between the CD4 T cell counts obtained with the Auto40 and FACSCalibur flow cytometers compared with the average CD4 T cell count, in absolute number (B) and in percentage (C). The full line represents the mean relative difference, and the dotted lines represent the superior and inferior limits of agreement. The arrow corresponds to the X abscise axis.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3293735&req=5

Figure 2: Results of 93 CD4 T cell count measurements from children aged less than 5 years and more than 18 months in the suburb of Yaoundé, expressed in absolute number (cells/μl) and in percentage carried out in parallel by the Auto40 flow cytometer and by FACSCalibur. - A and C. Passing-Bablok agreement test between the CD4 T cell count results obtained with the Auto40 and FACSCalibur flow cytometers, in absolute number (A) and in percentage (C). The diagonal dotted line represents the ideal line (no bias). The full line represents the regression line of the distribution; - B and D. Bland-Altman analysis on the relative differences between the CD4 T cell counts obtained with the Auto40 and FACSCalibur flow cytometers compared with the average CD4 T cell count, in absolute number (B) and in percentage (C). The full line represents the mean relative difference, and the dotted lines represent the superior and inferior limits of agreement. The arrow corresponds to the X abscise axis.
Mentions: The Figure 2 depicts the results from 93 CD4 T cell count measurements from children aged less than 5 years and more than 18 months, expressed in absolute number and in percentage. In this pediatric population, analysis of CD4 T cell count measurement expressed in percentage showed, similarly to CD4 T cell count expressed in absolute numbers, a high correlation and a close agreement between both CD4 T cell counting methods. Mean ± SD CD4 T cell count in percentage was 32.7 ± 12.1%CD4 (range, 10-70) by Auto40, and 33.0 ± 12.8%CD4 (range, 9-75) by FACSCalibur. The differences between Auto40 and FACSCAlibur were not statistically significant (P > 0.5). Results by Auto40 and FACSCalibur were highly correlated by regression analysis (r2 = 0.986, slope = 1.00, intercept = 0.0) (Figure 2, C). The relation between Auto40 and FACSCalibur did not differ from linearity (P > 0.5). The Auto40 results showed a bias of -0.30%CD4+ (95% CI: -0.91 - 0.31) as compared with FACSCalibur (Figure 2, C), thus demonstrating a close agreement between both methods to measure CD4 T cells in percentage.

Bottom Line: A FACSCalibur flow cytometer (Becton Dickinson Immuno-cytometry System, San Jose, CA, USA) was used as reference method.Bland-Altman analysis showed a close agreement between Auto40 and FACSCalibur results expressed in absolute count as in percentage in Yaoundé and Ambang Bikok.The Auto40 flow cytometer installed in a therapeutic mobile unit and operated far from its reference laboratory gave a perfect correlation with the reference method, and could be useful in carrying out immunological monitoring of HIV-infected patients living in areas without access to laboratory facilities.

View Article: PubMed Central - HTML - PubMed

Affiliation: Laboratoire National de Santé Hygiène Mobile, Ministère de la Santé Publique, and Faculté de Médecine et des Sciences Biomédicales, Université de Yaoundé I, Yaoundé, Cameroun. fxmkeou@hotmail.com

ABSTRACT

Background: A mobile health unit may be useful to follow up adult and pediatric patients on antiretroviral treatment and living in remote areas devoid of laboratory facilities. The study evaluated the use of the simplified, robust, single-plateform, volumetric, pan-leucogating Auto40 flow cytometer (Apogee Flow Systems Ltd, Hemel Hempstead, UK) for CD4 T cell numeration in a mobile unit, compared against a reference flow cytometry method.

Methods: The therapeutic mobile unit of the Laboratoire National de Santé Hygiène Mobile, Yaoundé, Cameroon, was equipped with the Auto40. A FACSCalibur flow cytometer (Becton Dickinson Immuno-cytometry System, San Jose, CA, USA) was used as reference method. EDTA-blood samples from volunteers were first subjected to CD4 T cell count in the mobile unit, and an aliquot was sent within 4 hours to Centre International de Référence Chantal Biya, Yaoundé, for FACSCalibur assay.

Results: Two HIV screening campaigns with the mobile unit were organised in December 2009 and January 2010. The campaign in the suburb of Yaoundé which was 20 km from the reference laboratory included 188 volunteers comprising 93 children less than 5 years old. The campaign in Ambang Bikok (53 km far from Yaoundé) included 69 adult volunteers. In Yaoundé suburb, mean ± standard deviation (SD) CD4 T cell count was 996 ± 874 cells/μl by Auto40, and 989 ± 883 cells/μl by FACSCalibur; in Ambang Bikok, mean ± SD CD4 T cell count was 1041 ± 317 cells/μl by Auto40, and 1032 ± 294 cells/μl by FACSCalibur. Results by Auto40 and FACSCalibur were highly correlated in Yaoundé (r(2) = 0.982) as in Ambang Bikok (r(2) = 0.921). Bland-Altman analysis showed a close agreement between Auto40 and FACSCalibur results expressed in absolute count as in percentage in Yaoundé and Ambang Bikok. When pooling the 257 CD4 T cell count measurements, the Auto40 yielded a mean difference of +7.6 CD4 T cells/μl higher than by reference flow cytometry; and the sensitivity and specificity of Auto40 in enumerating absolute CD4 T cell counts of less than 200 cells/μl were 87% and 99%, respectively, and in enumerating absolute CD4 T cell counts of less than 350 cells/μl were 87% and 98%, respectively. The intrarun and interun precisions of the Auto40 assay assessed in the mobile unit were 5.5% and 7.9%, respectively.

Conclusions: The Auto40 flow cytometer installed in a therapeutic mobile unit and operated far from its reference laboratory gave a perfect correlation with the reference method, and could be useful in carrying out immunological monitoring of HIV-infected patients living in areas without access to laboratory facilities.

Show MeSH
Related in: MedlinePlus